Lighting fixtures, such as troffer-style lighting fixtures, are ubiquitous in industrial spaces, such as warehouses, and in commercial office spaces. Many of these lighting fixtures house linear elongated fluorescent light bulbs, or more recently light-emitting diodes (LEDs), that span the length of the troffer. Such lighting fixtures can be mounted to or suspended from ceilings, and some can be at least partially recessed into the ceiling.
Visible Light Communication (VLC) is a data communications variant which typically utilizes visible light between 400 and 800 THz (780-375 nm wavelengths). VLC is a subset of optical wireless communications technologies, and typically uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kilobits per second (Kb/s). Or it can use light-emitting diodes (LEDs) to transmit signals up to 500 mega-bits per second (Mbit/s). Mobile electronic devices which generally contain a camera or image sensor (such as an array of photodiodes) are operable to receive the signals from the light sources. VLC can be used as a communications medium for ubiquitous computing, because light-producing devices (such as indoor or outdoor lamps, television monitors, traffic signs, commercial displays and/or car headlights and/or tail-lights) are used everywhere.
In some applications, VLC permits a user with a mobile device that includes a camera (such as a smartphone or a tablet computer) to determine his or her location (for example, a location within a warehouse) by use of a signal transmitted from a light fixture. However, because of limitations involving the field of view and pixel density of a physical camera, the light fixtures need to be placed at a close proximity to each other (in a high density array) so that nearly one hundred percent (100%) coverage can be achieved.
Therefore, it would be advantageous to provide a method and apparatus having an improved effective pixel density and field of view so that the required light fixture density can be decreased while still allowing for the possibility to achieve applications with 100% coverage.